The use of the flow-directed balloon-tipped pulmonary artery catheter is now well established in clinical practice. It was initially described in 1970 in the important paper by Swan, Ganz et al., "Catheterization of the Heart in Man with Use of a Flow-Directed Balloon-Tipped Catheter", New England Journal of Medicine (N.E.J.M.), 283, 447-451.
The uses for this device range from the management of critically ill patients in the Intensive Care Unit to the monitoring of patients for open-heart surgery, diagnostic cardiac catheterization, and research applications. The device can be used to measure central venous, pulmonary artery and wedge pressures.
The Swan-Ganz catheter equipment and the accessories often employed with it are described in many medical publications, including, for example, the following:
Anaesthesia 34, 651-656 (1979), "The Swan-Ganz Pulmonary Artery Catheter", and Anesthesiology 45, 146-155 (1976), "Hemodynamic Monitoring: Invasive Techniques".
In the operating room and in the intensive care area, the Swan-Ganz, balloon-tipped, pulmonary artery thermodilution catheter is often used for the measurement for intracardiac, intraarterial, and intravenous pressures. Often this use is combined with use for the administration of intravenous fluids and medication. For these purposes, the catheter generally is provided with a thermistor sensor, a distal lumen for pulmonary artery pressure measurement (the lumenal opening generally being at the tip), a proximal lumen generally located about 30 cm from the distal lumen for central venous pressure measurement, and a balloon tip for flow directing. This catheter has become standard for the care of patients with medical histories demanding the careful regulation of fluid balance and for the measurement of cardiopulmonary performance in the operating room and in intensive care.
To use the catheter, it is inserted percutaneously, generally with the assistance of an introducer cannula. The distal lumen is connected with a pressure transducer for monitoring the pulmonary artery pressure. The distal lumen can also be used for mixed venous blood sampling. If so designed, it can be used for the measurement of cardiac output by the thermal dilution principle. It can also be used for the administration of drugs or agents likely to cause phlebitis or which it is desirable to direct in a concentrated form into the heart or great vessels.
The prevention of blood clots in the catheter system is achieved by continuously flushing both lumens with sterile solution. This is usually accomplished by the connection of intravenous fluids to the proximal lumen port and the distal lumen port to the transducer flush system. A schematic diagram illustrating the technique for connecting the transducer appears in the article in N.E.J.M., supra.
In addition, fluid may be injected into the proximal lumen for the determination of cardiac output by the thermal dilution method, and blood may be withdrawn from the distal lumen for the determination of intrapulmonary shunt fraction. Such data as the pressure measurements referred to, cardiac output, intrapulmonary shunt, and body temperature are utilized for the diagnosis and treatment of conditions arising in the operating room and in the intensive care unit.
In current practice, since the central venous pressure measurement is required less frequently than the pulmonary artery pressure measurement from the distal lumen, a single transducer is commonly connected to the distal lumen and a single intravenous solution is connected to the proximal lumen. When the central venous pressure is to be measured, the transducer tubing is disconnected from the distal lumen, both parts being held in the hands, and the intravenous tubing is also disconnected from the proximal lumen, these tubings being placed on the patient's bed. The tubings are then reversed, the intravenous solution being connected to the distal lumen, the transducer being connected to the proximal lumen, and central venous pressure then being measured. The process is reversed to establish the original conditions.
In addition, it is common practice to place additional stopcocks and tubing in the system, to permit the injection of fluid for cardiac output measurement, and for sampling of blood for intrapulmonary shunt determination. These stopcocks are known to be sites of contamination of catheter systems, Anesthesia and Analgesia, 55, 141-142 (1979), "Stopcock Contamination". There is always a risk of malpositioning one of the stopcocks, a risk of the entry of air into the system, or of the production of blood clots in the catheter, rendering the catheter non-functional and subjecting the patient to the substantial risks of catheter replacement which include ventricular extrasystoles, heart block, ventricular fibrillation, intracardiac knotting, balloon rupture, thrombus formation and pulmonary infarction, perforation of the pulmonary artery, and infection, Anaesthesia, 33, 172-177 (1978), "Hazards of Central Venous Pressure Monitoring". In addition, the catheter should be firmly stitched in place, and all devices attached to it preferably should have locking hubs.
At present, there is no available valve design which permits these measurements, injections or sampling to be made through the operation of a valve, simply, safely, and with the necessary degree of sterility. Accordingly, each time a reversal of the tubings is done, the patient is placed at significant risk for the introduction of bacteria into the catheter and consequent bacteremia, sepsis, and endocarditis. When an array of stopcocks and tubing is used, the arrangement is often baffling, even to its designer, leading often to confusion and sometimes to errors on the part of personnel who must monitor the patient and use the arrangement on a 24 hour per day basis, especially when the designer of the arrangement is not at hand to explain it. Seldom are these arrangements uniform in structure or function, so that each requires study and sometimes experimentation. All of these considerations can generate potentially life-threatening complications for the patient.
In the intensive care area and in the operating room, such procedures may be repeated up to 30 times per day per patient, thus exposing the patient many times to these risks.